A growing scholarship argues that decarbonization cannot be achieved with single instruments like carbon pricing alone. A broader mix of reinforcing policies is required. This literature focuses on how policies can accelerate technological innovation, restrict polluting activities, promote green growth, and ensure social justice. Applying the policy mix literature to the European Union (EU), this article examines the development of climate- and energy policies from separate and narrow initiatives to coordinated policy packages to achieve increasingly ambitious climate targets, culminating with the European Green Deal. The starting point to explain this policy development is that EU policies will reflect the positions of the ‘least ambitious’ actors when unanimity is required. Examination of different policy phases shows that EU policy mixes are not only needed to fulfil different transition functions – they also provide opportunities to combine different actor interests to raise climate ambitions. The EU institutions have been instrumental in crafting policy packages that exempt and compensate the least climate-ambitious actors. The Paris Agreement has also provided an enabling context for higher EU ambitions. Looking towards the future, the corona-induced recession has so far mainly been used by the EU as an opportunity to strengthen climate ambitions and the European Green Deal.